1. Field of the Invention
This invention relates to lubricant compositions having improved rust inhibition and in particular to oil compositions containing a mixture of oil additives.
2. Discussion of the Prior Art
A desirable function of lubricants used in automotive, marine and railroad engines, or in other engines, is the ability to prevent rust of the metal parts. Such rust is often caused by moisture which usually condenses from the atmosphere and collects inside the engine. It is known, however, the unmodified lubricants, such as lubricating oils, or greases made therefrom, will not prevent the formation of rust on the metal surfaces with which they are in contact. Therefore, a great deal of effort has gone into the development of an additive, or an additive system, that will control rust formation.
One example of the oil additives that have been used as rust inhibitors are the metal sulfonates, both neutral and overbased complex sulfonates. Reference to U.S. Pat. Nos. 2,616,911, 2,721,843, 2,739,124, 2,856,360, 2,861,951, 3,658,703, 3,155,616 are examples of those patents that teach typical preparations of the overbased metal sulfonates.
Other useful rust inhibitors for use in lubricants are the naphthols or polyhydroxy naphthalenes.